Neurological disorders include acute brain or cord injury such as stroke and chronic aging and several neurodegenerative disorders such as Alzheimer's disease, Parkinson's disease and Huntington's disease. Neurodegeneration relates to the progressive loss of structure or function of neurons, including death of neurons. Many neurodegenerative diseases occur as a result of neurodegenerative processes. Currently, no effective therapies exist that provide either protection or restoration of neuronal function for neurodegenerative diseases. Many clinical efforts to provide such benefits by infusion of neurotrophic factors have failed in spite of robust effects in preclinical assessments. One important reason for these failures is the difficulty, due to blood-brain-barrier diffusion limits, of providing these protein molecules in sufficient amounts to the intended cellular targets in the central nervous system. A great need exists for the development of a novel therapeutic approach that promotes an axonal regenerative response where axons are able to regrow, reach their targets, and restore function.
Metallic nanoparticles have been intensely studied due to their unique optical, electrical and catalytic properties. To utilize and optimize chemical and physical properties of nano-sized metal particles, a large spectrum of research has been focused on control of size and shape which is crucial in tuning their properties. Several approaches are in practice to synthesize metallic nanoparticles such as UV irradiation, laser ablation, aerosol technology, lithography, ultrasonic fields, and photochemical reduction techniques. US 20100068240 discloses implantable nerve regeneration conduits that mainly comprise a biodegradable polymer and a metal, wherein nanogold is used to enhance the physical strength of the conduit or facilitate nerve regeneration by increasing the amount of BDNF and GDNF released from glia cells. However, the nanometal used in US 20100068240 is to enhance the strength of the implantable conduit and stimulate glia cells to release BDNF and GDNF; however, this prior art reference neither teaches nor suggests the direct increase of neuron growth and treatment of neurological disorders by metal nanoparticles themselves. Seungmoon Jung et al. disclose that intracellular gold nanoparticles increase excitability and aggravation, whereas the reference shows that intracellular AuNPs led to abnormal firing patterns and aggravated epileptic activity under pathological conditions, thus suggesting a possibility that intracellular AuNPs can cause or worsen neuronal dysfunction or damage in the brain (Seungmoon Jung et al., PLOS ONE, Vol. 9, Issue 3, e91360).
Therefore, there is still a need to develop an approach to promote neuron growth/outgrowth and treat and/or prevent neurological disorders.